The present invention relates to an apparatus for setting a work coordinate system on the basis of a position (program original point) from the surface to be machined of a work in which stock allowance is taken into consideration at the time of machining the work by a machine tool, particularly, by an NC machine tool.
A conventional NC machine tool has two coordinates for machine control and work machining, and before machining, the position of the machine coordinate system is first ascertained and thereafter the variation of a work mounting position (program original point) with respect to a machining program is manually corrected as the set value of the work coordinate system.
However, the above-described manual correction requires instrumentation, manual calculation, and complicated machine operation. This fact brings about such problems as misoperation, long-term planning time and production of defectives. Furthermore, the problem as to on what work point (program original point) the machining program is based, and the problem of the program original point itself varying with respect to the machine original point depending upon the stock allowances and distribution of them prior to machining remains unsolved in automatization.
In addition, since the value of tool correction and the tool mounting dimension are processed collectively by the tool offset memory of an NC apparatus, the actual position of the blade tip of the tool on the machine coordinate does not agree with the data on the NC apparatus, and when the tool mounting dimension is offset, the variation often becomes large. Especially, occurrence of interference at the time of turret index by means of a turret of a tool rest is a great problem from the point of view of safety. It is also disadvantageous that the operation of the conventional NC apparatus is easily mistaken by the operator and is difficult in terms of controlling the tools.
Recently, various developments have been in progress to automatically set the work coordinate system, but in the present state of the art, no satisfactory apparatus for setting a work coordinate system has been completed.